This invention relates to copper-based alloys and, in particular, to an anneal resistant copper alloy having enhanced machining characteristics.
There are two basic types of copper and copper alloys commercially available today, namely, tough pitch (oxygen bearing) copper and oxygen free copper. Tough pitch coppers such as electrolytic tough pitch copper (C11000) and tough pitch copper containing silver (C114000) are known to have good machining characteristics. References to number designations for copper and copper alloys in this application will be to the (Copper Development Association Inc.) number designations. Such tough pitch copper alloys contain approximately 200 parts per million oxygen. The presence of oxygen makes such copper alloys unsuitable for severe cold working.
Oxygen free coppers, such as oxygen free copper (C10200) and oxygen free copper with silver (C10500), have enhanced ductility which permits severe cold working of the copper alloy. However, in some applications such as the production of commutators segments and in some punching operations, tough pitch copper must be used since the enhanced ductility of oxygen free copper makes it difficult to machine and further requires increased deburring after punching or machining operations.
Free machining copper alloys are commercially available. Two such alloys are tellurium bearing copper (C14500) and sulfur bearing copper (C14700). These alloys are commonly used in applications involving extensive machining such as in automatic screw machines or in operations where considerable metal removal is required. However, neither the tellurium bearing copper nor sulfur bearing copper alloys exhibit the anneal resistance of silver bearing copper alloys such as C11400 or C10500. Additionally, the free machining tellurium and sulfur bearing copper alloys do not have sufficient ductility to permit cold heading operations and/or severe bending of the alloy during fabrication.
Accordingly, the need still exists in the art for a copper alloy which has enhanced machining characteristics, good anneal resistance, and sufficient ductility to withstand cold heading operations.